Snowden, While on the Run, Poses Greater Risk to U.S.

WASHINGTON—The longer that National Security Agency leaker Edward Snowden stays on the run, the greater the danger to national security, U.S. officials say.

Mr. Snowden has said he has more information he may release, and U.S. officials fear that as he looks for refuge, foreign intelligence agencies may have the opportunity to access the material he claims he stole.